What's wrong with inviting Gilles Simon and Alize Cornet??? They have both certainly earned their invitations this year! Both are Top 20. Both are young and new faces.
Novak Djokovic was released from his commitment contract to the HC because both Ana Ivanovic and Jelena Jankovic were committed elsewhere. So he wanted to play, at least.
The HC has been forever attempting to bring back Roger Federer, especially since the tournament is turning 21! They are still trying to convince Patty Schnyder to play.
I have been waiting for a Marat and Dinara combination ever since she burst onto the scene. I'm glad they waited until Dinara matured as a player instead of rushing her in for the sensation factor.
Japan could be interesting with Ai Sugiyama and Kei Nishikori. Without Sugiyama, they will be invited to play the Asian Hopman Cup instead. Not that she's a huge international star or anything, just that Ayumi Morita (or whoever they choose) won't be enough to justify a main draw inclusion.
Andy Murray will most likely commit to Doha seeing as how he is the defending champion there. So the chances of Great Britain participating are slim.
The American team could be very strong this year. The HC will no doubt try to convince James Blake to return. If Serena plays too, then watch out. Or maybe Venus will play with Mardy Fish instead this year. How cool would it be to have Bethanie Mattek? haha
I can't see India taking part without Sania Mirza, and right now, she's too risky of an investment with her injury.
If the Czechs come back, it won't be with Lucie Safarova. She has been in terrible form this year, especially with injuries. Having said that, Nicole Vaidisova hasn't performed that much better either, but she is at least Top 30. Berdych probably won't play without Safarova, so it looks like Radek Stepanek is the next option.
Perhaps Spain are due for a return appearance? Anabel Medina Garrigues and Tommy Robredo again? Or maybe David Ferrer? A bit of a long shot would be Rafa.
Argentina are the best South American nation, and Juan Martin Del Potro has been playing exceptionally well in 2008, so he might be a possibility. The best Argentine female has been Gisela Dulko so she's in the mix as well.
Sweden? Belgium? Canada? Romania? Italy? Austria? I can't think of too many other possible countries that have both a top male and top female players. It's a shame that countries like China, Poland, Belarus, Ukraine, Denmark and Hungary don't have any top 100-ranked male players. It would be awesome to watch players like Li Na, Zheng Jie, Agnieszka Radwanska, Victoria Azarenka, Alona Bondarenko, Caroline Wozniacki or Agnes Szavay compete.
Then there's the Asian HC! I expect the top 6 combinations from China, Uzbekistan, Chinese Taipei, Thailand, Japan, India, Korea or Philippines to be somewhere in there.