My opinion on this is that we won't sign a star central midfielder this summer. I think we may strike a deal with Spurs, that they keep him this summer and if they don't qualify for Champions League next season (12/13) then we get first refusal on him.
I think Ashley Young is the replacement for Giggs as a winger, and with Giggs' performances in central midfield last season I think that will be his role this year. I also think this will be his last season and that when he leaves next year is when we'll go really crazy on getting a CM.
That said, the window still isn't even officially open yet so anything could happen - but that's my opinion on the whole situation at the moment.
Also, looking at Modric's stats since joining Spurs, they really are quite poor. Maybe we need something a little more, who chips in with more assists and goals than he does. Not saying he's a bad player - but with what we'd be expecting from him his 3 assists and 2 goals per season don't seem like they'd be of much use to us tbh.