Yeah, the next few years should be quite exciting from a NH perspective. Looking at the 6 nations sides:
Ireland should improve under a competent coach, although they need to develop a new centre partnership and sharpish, there's a few promising players in that department though.
England have all the makings of a great side, with an abundance of talent in most positions. Lancaster is just the guy to guide them as well, as long as he learn's from the mistakes he made last season of picking players out of position.
Scotland are improving, and for once have a backline with genuinely exciting players.
Wales are brimming with talent, but simply have to take that next step and start beating SH sides regularly, starting with the AI's. There are still a few issues regarding strength in depth in certain positions, but this is gradually improving.
Who the hell knows with France though!
Italy, I can't decide about. On the one hand a few of their influential players are on the wane (e.g. Castro), but they are developing a more competitive edge and challenging all sides. The lack of quality at junior level is a little worrying though.
Hopefully we'll see some hugely competitive 6 nations tournaments in the coming years, helping to drive all the sides forwards, further closing the gap between us and the SANZAR nations, although realistically that gap is only now apparent between us and NZ.