I would look toward where DL has a huge FF base, and what immediately comes to mind is BNA, MCI, AUS, PVD and JAX
I can see the first 3 getting AMS service, with the latter 2 getting seasonal AMS or CDG service. JAX is the shot in the dark though.
It likely is a consideration, but this should already play out in the route network from those cities, and so far the domestic route network has proved a decent predictor. I'm defining hubs/focus cities as ATL, NYC (JFK and/or LGA), BOS, DTW, MSP, SLC, LAX, SEA, RDU, CVG, and MCO, and please correct if I missed a route or two.
To use IND as an example, they have flights to all those cities except SEA and CVG (obviously).
CMH is connected to every DL US hub/focus with the exception of SEA, SLC, and (as with IND) CVG.
AUS - connected (or soon to be) to all major DL cities except MCO and CVG.
MCI - missing RDU, MCO, and SEA.
BNA - every hub/focus city connected or soon to be except MCO.
MKE - has SEA, CVG, and BOS but missing LAX, RDU, and MCO.
BDL is ATL/DTW/MSP plus CVG and RDU, not much route-wise (for obvious reasons no NYC/BOS).
TPA has all cities except SEA and MCO (for obvious reasons).
So, assuming six (the theoretical number of TATL routes this year) and also taking two off the board for IND-CDG and MCO-AMS, if I guessed I'd say AUS, TPA, CMH, and maybe BNA. All these cities (maybe excepting BDL) are small focus cities already so they already have the foundation to expand into non-DL stronghold routes if DL wants to grow them.
*edited for format