A lot of miners in China said yesterday that they will begin signalling for SegWit2X on Monday.
Here's what you need to know (before we get 200 ELI5 posts asking for this).
SegWit2X is both an agreement between many businesses and a software release intended to support the spirit of that agreement.
The agreement calls for two things to happen at two different times. First, to activate SegWit through a miner activated soft fork as soon as possible with 80% of the miners supporting it. Second, sometime later, to activate a 2 MB blocksize hard fork.
The software approach to achieve this, led by Jeff Garzik, is attempting to write one software package to accomplish both.
As an aside, if you told me I needed to deliver one complicated software feature soon and another complicated feature later, I would not try to deliver both simultaneously for the deadline of the first one. That seems like it would be obvious to a 5 year old. But to be fair to Jeff Garzik, there's politics involved in this thing being driven by people who don't understand software development, so that bit of stupidity is understandable. But this just shows why 5 year olds are smarter than a group of executives in suits.
For all of you though, SegWit2X has two very different things it's going to do at two different points in time.
First, the miners are going to try to activate SegWit alone, before the August 1st deadline set by the user lead movement known as UASF.
What do you have to do about the SegWit part of SegWit2X? You have two choices. One is to do nothing. SegWit is backwards compatible to all wallets. If you have a wallet that will support SegWit itself you also don't need to do anything because SegWit2X is actually trying to activate SegWit using the same code on your wallet. However, to ensure you are also enforcing SegWit activation you may choose to run either a UASF enforcing node or, if they make one available, a SegWit2X enforcing node.
Again, an aside from me, UASF nodes have had very few lines of code changed and the only change is that after August 1st, a block must signal in favour of SegWit to continue to be considered valid. SegWit2X has had a whole lot of changes – it is trying to see if 80% of miners are signaling in favour SegWit2X and if they are then it is going to try to reject blocks that don't signal for SegWit (and it has all sorts of hardforking code inside of it too that is meant to be dormant until some time in the future). I myself will be running a UASF node the whole time. I think that's reliable software. I know what it's going to do when it activates. And, the more of us that run it, the more incentive there is for none of the miners to betray their pledge to activate SegWit. I would not be surprised if many of the miners who have pledged support of SegWit2X actually instead choose to run the UASF because it does the same thing with way less risk of failure.
After SegWit is activated the first phase of SegWit2X will be complete. People will rejoice in the streets and there will be much merriment. Everyone on both sides of the scaling debate will declare victory. The price of bitcoin might go lunar.
Next comes phase 2, the 2MB hard fork.
Where you didn't have to do anything at all to get SegWit, you will have to take action to support a hard fork. In fact, a hard fork requires every single node to take action. Unlike a soft fork, a hard fork is not backwards compatible. SegWit2X will need to release software for every user to download and install and run for the 2MB hard fork to be universally supported.
The software task ahead of the SegWit2X team (which is really just poor Jeff Garzik and a few kind and not-so-kind code reviewers) is very hard. Testing a hard fork is extremely difficult. And testing on a test network is not the same as testing on the real world network. As bitcoin is constantly under attack by all sorts of parties, preventing an early activation or some kind of mis-activation can also be hard. The Bitcoin Unlimited hard fork client accidentally forked when it wasn't supposed to, for example, and it has a software development team larger than one person. Also Jeff only yesterday found out from a kind reddit user that the code he wrote to activate a hard fork didn't actually do that. If at this point you're thinking maybe you want a more careful approach to a hard fork you're on the same page as me. I do not oppose bigger blocks. I just want a very safe approach to any hard fork, if we're going to have one.
Anyhow, since this is bitcoin, you can expect all kinds of campaigns after the activation of SegWit to tell you that you have to upgrade and to tell you that you must not upgrade. There's even one proposal out today by one of the core developers that suggests that big blocks can be mined without a hard fork using a technology called a drivechain. The community will review that too and maybe something like that will satisfy everyone who matters in this decision.
The good news for everyone is that we are breaking through this scaling debate. Bitcoin will always be under attack and in debate. Don't sweat it. It can't be stopped.
This is already a lot of ELI5 information, so I'm going to wrap it up here.