It will stick. GW has confirmed this on several occassions. "The End times: yes, we mean it this time" from white dwarf being one of them. Im not sure if lizzies will be combined, I dont think we need to, or if it would make sense. even though I would love to make a Saurus "Count as" White lions with the new skink priest as a High Mage. Let alone make a Coatl "count as" Phoenix. In all cases I DO hope that they rediscover themselves as an independent race.
I see where you're coming from, but one of the End Times books (I can't remember which one, but I think Nagash) does mention some migrating Ogres working with O&G tribes. This could mean nothing other than a desperate end times alliance, however I can actually see them being compatible rules-wise, especially with GW supposedly cutting the excess rules of the 8th Edition to something more stream-lined and easier to get into. Fluff-wise, who says O&Gs would use the Ogres as mercenaries? I'm sure the Ogres themselves could see the profitability in exploiting a rampaging group of battle-lusting Orcs. Plus, aesthetically 'Ogres, Orcs & Goblins' generally sounds compatible. I'd be surprised if Ogres are left as a stand-a-lone army at any rate. Well, they did send a Wood Elf to create a new world in another dimension.. I can see the End Time staking more and more unexpected, contrived dramatic twists: "guys, the Old Ones never actually left, they just stopped inviting the Lizardmen to any parties after Kroak drunk too much punch". Or maybe the Chaos Gods are the Old Ones and the Slann all have amnesia...
Ogres have worked with pretty much everyone at one point or another. Even Chaos. Ogres are mercenaries. Reading their book, they have worked with almost everyone at some point, aside from Lizardmen. My local Tomb King player also names 1 instance where a tomb king dynasty hired ogres to assist him. They have a special character who have worked for orcs, before killing them all, and joining dwarves. They have worked with humans multiple times, etc. I think Skaven and lizardmen are the only two races who never hired ogres. Not sure about vampires, but considering their usual way of working, I don't see why they wouldn't.