I'm betting the 3.75" line isn't going to last much longer. Maybe a couple more series of DTC stuff, but everything's been done in that scale. I assume we'll find out during this weekend's con.
I guess that's why Sigma Six has two different scales, and neither are 3.75". I suppose Hasbro could have done some of the Sigma Six stuff in a 3.75" scale instead of 2.5", but such is Hasbro.