The franchise is still the same size as it was when Forza 4 was released. Forza: Horizon has sold poorly because it's not a mainline Forza game. It's as simple as that. I'm a huge Forza fan and I didn't bother getting it. Gears of War: Judgement and God of War: Ascension will also sell significantly less than their predecessors because they're not mainline games.
Anyway, 1 Forza game every 2 years is a good amount to keep the fanbase happy and not saturate the market. Any more than that and they're overdoing it.
Aaanyway, this is gonna start a flame war. Locking.
My prediction threads:
Wii U will sell under 40m units (made on 14th September 2012)
PS Vita will sell under 20m units (made on 30th September 2012)
Wii U will sell under 7m in 2013 - I was right
