I think A/S producing the iconic HST is most definitely a commercially viable option judging by the way they present their products to market. The number of livery options and varying specifications of the power cars is extremely large, then add in perhaps the iconic Mk3 coaches. I think the Hornby product is ok, but believe A/S could produce the definitive model, if their Deltics, Class 92s and Class 37s are anything to go by.
I also agree that the Class 31 and Class 50 locos are potential targets for A/S. Ironically, all three currently produced by Hornby. As Bachmann have just demonstrated with their new Class 47 project, A/S are causing some of these manufacturers to up their game. Great news for us modellers.
Fran mentioned back in March they were working on 'more than two new locos' and it sounded like it included another steam loco so hopefully after the Deltics are released we will get some exciting announcement...