I think you're worrying a bit too early. We currently know only 5 or 6 out of the many play sets they've planned. You don't really think they'd reveal
everything this early, do you?
And seeing as how Phineas and Ferb is such a popular show with lots of epic things going on (Especially for Perry), the likelihood of it getting a play set is very high. Just give it time. If we don't see a Phineas and Ferb play set within the next few years, then you may worry.
Just to make things clear, I'm not a Phineas and Ferb fan and I generally don't like tv cartoons... But I still think such a play set is very likely.