In my opinion, the common vision between XT, BU and Classic is that Bitcoin should be governed by the code people freely choose to run--and not by consensus parameters force fed by Core's central planners.
I think it is important to present a common and unite front in this respect. We want a hard fork to increase the block size limit, and we want to decentralize development away from Core.
XT was useful because it got the ball rolling.
Bitcoin Unlimited is useful because nodes can run it to express to the miners "I will accept bigger blocks today!" Nodes and miners running Bitcoin Unlimited will be compatible with miners running both XT or Classic.
If Classic gives miners the confidence to undertake a coordinate jump to 2MB, then I think that is a positive thing too.
Once the first bigger block rolls in, the "dam at 1 MB" will be broken. We'll know how to fork and it will be much easier to raise the block size limit in the future--and through a decentralized process to boot.
Regarding the question about merging implementations, I think the word "merging" is somewhat ambiguous at this point. But I do believe that the individuals behind each of these implementations want to work cooperatively for the betterment of Bitcoin. I know I do. I want to help create software that users want to run and that miners want to mine with. Whether it will make the most sense to converge on a common GitHub repo, or have several projects running in parallel, is not clear to me at this point in time.
The present focus should simply be working together to get that first 1.1 MB block into the blockchain and to win nodes away from Core.