Yes, there is a next-generation Area 51 on the drawing board. It is very early in the design phase, so there's not really much to say about it. I wish I could indulge you in premature, wild speculation, but the design is still developing and changes literally every day. Besides, too much peeking under the covers takes all the fun out of a big launch!
For the existing proposals, I would just continue as normal. When this new process finally launches, it will quite literally put anyone who wants a proposal so far and ahead of where they are now, no one could possible feel like we've set them back at all. Even if its not ultimately the current "Area 51 process" that launches your site, you are still gathering ideas, building consensus, and finding an audience to help build your site. This doesn't change any of that.
As for the ETA, it's still way too early to say… but its almost certainly in the "months" time frame. It's not going to be weeks; it's not going to be years.