Gulf was at the ELMS test day and ran both their Vantage and the McLaren (which had ELMS numberboards on it) and I've got a good feeling they'll likely run one car in Pro with some McLaren factory drivers and support (Bell, Parente, etc) with Roald and Stuart in an Am car.
Hexis is likely to go BES next year but with the drivers they have and the likely factory support they'll get I've no doubt they'll be in GTE in 2014 (BES in prep for longer races?).
And United....well they've also got some pro's and have had the intention for a long time to race at Le Mans and ALMS so I wouldn't put it past them to go GTE.
All speculation however...