The issue with any future run of the E7 has to do with larger numbers than any single railroad can provide. Another run is probably, and I'm only guessing, about 500-700 units. The minimum run per road was 40 units. It may be to 60 now, but I can't pretend to speak for Scott's production requirements with the manufacturer as that is a moving target. 40 units of PC in 2r and 3r would probably sell on a future run if someone wanted to front the costs and could hold a portion of the inventory. If I were going to get a future E7, it would be PC and in 3 rail. While my 2 rail layout is 1953-1957 era specific more or less, my 3 rail is a pretty loose 1972 to 1982 time period. A lot happened then!
Since there have been two full runs of E7s and some specials. The question is now, what road names that haven't run would fill in the rest of the run? As much as I'd be interested in one, I suspect we won't see another run of E7's from 3rd Rail anytime soon if at all. The FL9 tooling is the next generation and an evolutionary improvement. The FP7 will be as good or better 
Your best bet is to lobby for those as a special run through a dealer. Many FP7s ran up into the Conrail era and would be a nice fit for most three rail layouts with the shorter wheelbase. Eight road names for the first run are being settled by preorders as we speak. Your pre-order is your vote 
While I'll likely get a set of Tuscan 2R units. I'd be in for a PC 3 rail one it if happens. Of course, I'd prefer Amtrak ....... LOL.
