I don't see Bent going to a bigger club than us. No disrespect to him, but he's not the sort of forward that one of the top 6 would want. Spurs tried, but didn't want to play him over Defoe. Chelsea, Utd or Arsenal wouldn't sign him. Liverpool possibly. Man City wouldn't find him internationally marquee enough.
If we slip down the rankings over the next few years and someone with investment rises, then he could well see a bigger club to tempt him away. But in all honesty I think we're the biggest club that he'll be at. Anywhere else will be a sidestep at best. Personally I think he knows that, and I'm delighted we've got him. I fancy we'll see Bent here for a couple more years. If anything, he'll leave on our terms if his form slips, or another manager wants a more all round, team player up front.