Not meaning to pour water on this but I remember a couple of years ago he told Star Trek Magazine on why he would not appear in Doctor Who saying that he already done enough sci fi with TNG & X-Men.
Anyway whatever the reason for his change of position on Doctor Who, now that he has expressed an interest I hope he does get a role in it.
In the meantime he will be appearing with David Tennant on stage in Hamlet next year.