A [change-request] is much like a [feature-request] in meta. Getting it implemented is part gaining popular support, part looking at the merit of the idea… and part getting around to implementing it.
On the surface, the proposals you linked all sound like reasonable candidates. But there's certainly no shortage of proposals needing attention in Area 51. My highest priority would be the Skepticism and Skeptic Exchange proposals because of the imminent creation of the latter.
As an aside, there really hasn't been any physical merging of proposals. The process is just too fraught with problems; for example, people suddenly finding themselves following a proposal they did not select. Some proposals simply have to to compete and people should be free to choose. But there comes a time where one proposal gains the momentum — when it's time to contact the other proposal followers to unite support a single proposal.
So, to answer your specific question — how long — progress will start out a bit slower at first, while I organize these discussions and get a bearing on how these forums will result in useful changes. But you are being heard and the changes will be made (or declined) before some half-baked idea creates an ill-conceived site. Remember what the end game is here: To make sure Area 51 is creating successful sites.