@willbsn13 - Glad you brought it up. I've actually been a proponent for the GaaS model, since it makes a lot of sense for the driving genre. I don't think (or want) console games to go to the expensive lengths of iRacing, but I do think a change from the current approach could benefit Forza.
For one, it'd avoid franchise fatigue. Look at GTA5: it's 3.5 years old, but still has quite the dedicated player base thanks to constant updates. Sure, some people complain about the (in-game) expensive additions with each new update, but I think it's a much more generous approach than if Rockstar had just given up a year in, to produce another largely similar game 24 months after release. Or made every update a paid DLC pack.
I haven't played it, but Street Fighter V apparently has a similar approach: you can buy the DLC characters with real cash, but you can also win them in-game. I'm sure it's a slog to do, but it's a considerate approach IMO: there needs to be a balance between profitability and gamer-friendly practices.
Racing games, especially those leaning towards the sim side of the scale, don't have story lines. There's no functional reason for a sequel if all that's been done is additions onto the base that was the previous game. I suppose in the case of FM5->FM6, there were a lot of small detail changes to accommodate a 50% increase in field size plus new weather, but it's still running off the same engine.
The main issues I see that model needing to overcome is a (likely) aversion from a large percentage of the existing community, and the question of how much less profitable it may be versus the current hard two-year format. But imagine if both Forza franchises adopted a 3-year plan and had a longer support period? I know I'd like it.
There also needs to be some sort of cost-effective way to split DLC across both franchises. Every time an FH3 pack is unveiled, I think "man, I wish I could run that car in FM6." I'm sure I'm not alone, and T10 needs to figure out a way to support both titles concurrently, in a way that boosts profits for them without alienating the fanbase.