The teebird will never be left behind, simply because there is no other disc that can duplicate its flight path and is so consistent across all the plastics that it is made in. The PD doesn't really fly like a teebird, it has too much high speed turn and the S/Cs have too much low speed fade. For comparison, the OLF is pretty much a duplicate of the eagle-x in a faster speed, and those two discs are much much closer in flight characteristics than the PD and teebird are.
I thought I could move away from teebirds as my game progressed. Tried the PD, didn't like trying to power down on them. Just not as good as lower power shots as a beat DX Teebird. Tried the stalker, but couldn't get the same distance out of them without really throwing harder than I wanted to. Tried the OLF, and while an amazing disc, it's more of a distance driver - and the hard to find 1.1s were the best iteration to this point. I'm back on the teebird now, and I pretty much always have a champ, star, new/beat dx in the bag all the time. I will say, however, that the S-FD is really very similar to a beat DX teebird. I'll probably continue to cycle dx teebirds along with the FDs, but mainly because of the natural progression of throwing a new one so often.