Steph would probably be better next year. I don't think you can lose your jumper that fast (a lot of people were saying that he lost a step, but the primary problem was teams were defending him like Rondo and, in response, he shot worse than Rondo). It's just he doesn't fit too well. We already have 2 other back-ups signed at that spot and none of them, including Steph, can really switch over to the 2 guard. We could still use him, but it would probably be around 10 mpg, and we'd probably have to utilize the iffy Steph-House combo more than would be wise to make best use of our bench.
There are three other options that make more sense.
First, try and get a playmaker at another position so we can continue to use House at the 1. Grant Hill would be great. Second option would be to add more shooters, especially at the big positions, too space the floor better off the bench and make Pierce more effective in a pseudo 6th man role, where he gets subbed early and then comes back to anchor the bench scoring. A third option would be to add a big PG who can defend 2s and penetrate on offense. These aren't very common and they're usually pretty expensive. Keyon Dooling would be nice if we could get him in a trade. Marbury, or any other small playmaking guard, should be the fourth option.