Doubtful. If FM5 comes in about 2 years on the 720, I doubt we'll be getting night *and* weather. Actually, I think we will be getting neither of them.
I don't know, I tend to disagree on this one.
We all know that all in-game engines and probably assets from PGR series have been turned down to T10 after Bizzare left Microsoft. Also, at one point there was a gossip how T10 will actually continue to develop PGR series and we have also see assets with night/rain concept art in T10 studio overviews.
We also know how all this-gen engines (both graphics/audio and physics) are made to fit the constraints of current hardware but how actual assets originally made for this-gen games are in much higher quality than one we all get in final products.
My presumption is how T10 probably experiments with both Bizzare's engine and their own engine on some placeholder hardware for next-gen. Also notice how Codemasters already achieved a crazy level of development for their EGO 2.0 engine used in both Dirt 3/F1 2011 which already can do 24 destructible cars (graphically 25 with Safety Car) on track with open-wheel geometry and suspension animation and modeling, progressive mechanical damage modeling, high-res textures, fully animated drivers, fully animated cockpits with lighting and shadowing and full weather cycles and day/night cycles (notice how Abu Dhabi GP in F12011 will have day/dusk/night transition) with interchangeable skyboxes. All above can be run on 1080p/+60fps on decent PC with no problems. So, even current-gen engine can run everything we want from this gen driving games, only constraint is the 2005 hardware in consoles.
To cut long story short, I would be really disappointed if any of AAA racing titles on next-gen hardware doesn't come with all mentioned above. However, since GT series already presented all above on this-gen consoles - although with some problems, but goal is achieved - I would presume how roughly 4X more powerful hardware will allow that driving games come with all we want from them.
I can fully understand how current-gen hardware is limiting in every way imaginable but how possibility for them probably exists in every engine currently on the market. Slight return to past says how Codemasters introduced variable daytime changes even in EGO 1.0-powered GRID (on LeMans tracks), first TDU had pre-baked time of day that run in real-time, TDU2 introduced real time daytime and weather changes, Rockstar did the same with their GTA/RDR/Midnight Club engine, Eutechnyx deployed the best looking rain-effects on their PS3 racers Ferrari&Supercar Challenge games, I already mentioned PGR engine... and list goes on. But only constraint was 30fps because of insufficient hardware power, only being successfully tackled by Polyphony Digital through crazy programming.
In conclusion, engines to achieve everything already exist and it would be really surprising not to see them shine in full glory on the very beginning of next-gen lifetime.