The Australians who look like they will get in or close to top 100 over the next two years:
Chris Guccione - Just a matter of time, only needs one semi-big result to get in.
Nathan Healey - After dissapointment of losing so many points from the aus open and dropping into the 200's, has made huge strides to get himself in the 180's.
Peter Luczak - Lost a lot of points from the aus open and needs to win a couple of challengers.
Mark Philippoussis - maybe thats all im saying.
One that's really exciting me and has jumped 1000 spots in the rankings this year is
Greg Jones - only 18 but reached the final of the Burnie Challenger and is looking like a big hope for the Aussies.
In five years time expect to hear the name Bernard Tomic as the next big thing.
There are several Aussies on the way up, but most of the guys you listed are longshots to make a real impact.
Chris Guccione certainly has a good chance to make the top 100, but I don't think anyone foresees him even coming close to becoming the successor to Hewitt's stardom. He'll be a decent ATP player, but probably nothing more.
I'm actually a fan of Nathan Healey, but I don't think he has a great shot. His 3R appearance at the 2006 AO was more luck than breakthrough - he got a retirement against Volandri and then barely beat Amer Delic. Not exactly big-time wins. He did win Burnie this year, but along with the Ecuador challengers, it is one of the ultimate Mickey Mouse challengers - close to a future than a real challenger, actually. He'll have to show me more to make me a believer, but time is rapidly running out for him (he turned 27 yesterday).
Luczak...even older than Healey. He came close to the top 100 in 2005, but now his form has declined and he's out of the top 200. He seems to be a player on the way down, not the way up.
Philippoussis - if he can stay healthy, sure, but we've been saying that for a long time. If he does come back, it won't last since he's already in his 30s.
Greg Jones - Now here's an actual prospect. He only just turned 18, so his results have been quite encouraging. He'll definitely be one to watch on the futures circuit this year.
Brydan Klein - Won the AO Boy's title. I didn't expect this from him, but he'll be another guy to watch on the futures circuit. 11 months younger than G. Jones.
Nick Lindahl - currently about 18.5 years old and just outside the top 300. This year is a big year for his prospect status - if he can break through to be a challenger regular it would bode well for his future - if he stalls in futures/challenger qualies, his star will look a lot dimmer.
There a few other moderately interesting types further down, and then there's Tomic. Australian tennis is not totally awash in young prospects, but with the emergence of Lindahl, Klein, and Jones, at least there are youngsters to watch, which is an improvement on following journeymen like Sirianni, Bourgeois, A. Jones, Nettle, etc who all are just trying to be the next Nathan Healey.