As we're discussed before, I disagree.
Watson is only 24, and is in my opinion one of the most promising players going around anywhere as things stand. He's not ready for test cricket yet, but he's got a heap of talent with the bat (enough to be a specialist test batsman, for me), and with the ball he's got a lot of work to do but there's potential there as well. Most players peak in their late 20s with the ball and their early 30s with the bat, so I'd not be panicking yet.
People who write him off now do so at their own risk, because frankly there's nothing to judge him on yet. If you judge him on his FC record obviously he has done very well, but that's not international standard. If you judge him on his ODI record he looks pretty poor, but he's been played in a role alien to him, and his game is not suited to the limited overs format anyway. There's nothing to judge him on in tests yet.
Furthermore, it's important to remember that his role in the test team, should he make it, will be either a specialist batsman or a batting all-rounder batting around 6. That is the role he's suited to, not batting at 8 as a bowler who can smack the ball around at the death, which is what he's being used for in ODIs. I still think he can become a good ODI player, but he's not there yet and he was never someone you would immediately expect to succeed in that role.
Give him time and plenty of domestic cricket and hopefully a season or two without any injury troubles, and then if he's still performing and there's a space available, give him a run in the test squad.