Or you can just deal with sharding for a week or two and save the hassle of trying to shove several different set communities together after the fact.
They aren't going to do this, they are going to shard the servers early to actually try and keep as many dead servers from possible happening.
I have yet to figure out how anyone thinks ripping communities apart after months is a much better option than not seeing a few people for a week or two. Needing to do server merges is actually a worse idea.