On a related note, apparently one of the names on the very short list for the 11th Doctor was Nathan Fillion.  Take that as you will but he could have been an interesting choice.
Regarding Torchwood US, reading between the lines, I suspect the ongoing problems with it may be why Torchwood is in limbo at the moment.  A little while ago BBC Wales announced their slate of ongoing drama and whilst Doctor Who and The Sarah Jane Adventures were on it, Torchwood wasn't.  Personally, I hope the US version takes off because done right, as it clearly was in Children of Earth and chunks of season two, it's a great show.  
It'd also be possible to do the same sort of thing Primeval was, and as far as I know, is still planning with foreign remakes.  Namely, it's not a remake, it happens in the same time and universe as the core show, just in a different country.  In fact, one of the things Torchwood has always desperately needed, to me anyway, is some form of internal connectivity, and having a reference to the Torchwood US office, and Jack flitting between the two, would be interesting to see.