bhomburg

By then, the all JBA (AA, BA, IB, AY) transatlantic flights should have lie-flat seats in business class, so it should be scheduled on equipment with these seats.
There's basically three options as to what can happen to this flight come the beginning of 2016:

1.) The route will get a refurbished 777-200 ("77D") with two classes of service. The J product on these is vastly improved with all-aisle-access lie-flat seats and pretty much state-of-the-art. However, given the way-behind-schedule of AA's 772 CIP program, aircraft swaps to an old three-class one are very common.

2.) They'll put a refurbished 763 on it. Business class on these is decent, but not special: you'll get a lie-flat seat with all-aisle-access. It's not as spacious as the 77D, though - the seats are pretty narrow and don't work that well for above-average-sized people especially those with large feet.
3.) It goes 787, which personally I think is rather unlikely.

This flight went from 763 to 772 and back four times since I started flying the route on AA regularly some five or six years ago, most of the time with very little notice - so I would not count on anything.

Personally, I would book F and see what happens just to be on the safe side. I could see availability on a few days next May.
You can always downgrade in case it gets swapped out to a two-class plane, or opt to be rerouted via LHR, where F continues to be available if you don't like the aircraft on offer that day. AA are actually pretty good about this, and have rebooked me twice before on this route when planes were downsized.

If you would consider connecting itineraries or only see availability with connections, you can:

- fly to LHR on AA and connect on BA. There's several DFW-LHR flights a day, and at least one of them is scheduled to be operated by AA's flagship 77W, which has F and a really nice business class seat. The other two flights currently are scheduled on 777-200s, and the chance of getting a refurbished one is probably highest on this route.
Disadvantages: The connecting flight on BA is nothing special at all, and the transfer experience in LHR (you need to change terminals) can be a real nuisance. Also, there's higher taxes/fees, as LHR is an expensive airport to transfer in plus the BA YQ surcharge on the intra-European segment. Also, you run the risk of getting an unrefurbished 772 as equipment substitution, so I'd book F just in case...

- fly to LHR on BA F and connect on BA. While BA's business class is nothing to write home about, their F cabin is nice. The connection experience in LHR will be good and - especially if your dad hasn't ever flown premium before, the whole journey will qualify as "special". You'll have access to the Concorde Room lounge in LHR, and the transfer experience is much nicer ona a BA-only journey thanks to not having to change terminals.
This carries very high fees/surcharges, though.

- fly to MAD on AA or IB and connect on IB or LAN (the LAN flight is a 787 with a real nice business class cabin that continues to FRA after making a stop in MAD from SCL. If the timing works and there's availability, go for it). You will need to call AA to check availability - IB flights are not displayed on aa.com. Business class on IB is OK, and fees are not outrageous.

- make a domestic connection to PHL, CLT or MIA and fly to FRA from there on the legacy US Airways A330-200 (PHL, CLT) or an AA 763 (MIA). The US Air experience may not be "special" but the seat is very nice (a somewhat more budget execution of the same seat AA chose for its 77W planes with all-aisle access, good privacy and space). This has very low fees.