The funny thing is that Sehwag, unlike Slater, has demonstrated the ability to bat in ODIs over an extended period (his scoring throughout 2002 having been pushed up to the top of the order was superlative). Sehwag is also a manufactured opener, Slater was a natural one.
I do still have hope for Sehwag - in his recent ODIs (last 10 or so) he's batted in just about the perfect way. He's smashed the weak bowling (of which there's been plenty) but has realised that in order to have his best chance of smashing the crap stuff, he needs to treat what good bowling he receives with respect. For ages (ie, throughout 2003, 2004, 2005, 2006, 2007 and the first half of 2008), he wasn't doing that. If he can keep batting the way he has been in ODIs recently, he'll be quite a force once again.