I dont think its too early to judge him. I've seen a fair bit of him & has i mentioned before he is journey county pro basically. He averages 36 in FC cricket, which basically tells you the whole story about him. Thats not the sort of FC bowling average that would get one excited about a players chances of being a international success.
The spin cupboard in England is crap behind Swann. Atlhough the only/main reason Tredwell was picked because he seemingly impressed the selectors on the lions tours recently & a decent FC season in the poor Division 2. As i said he could be useful againts Bangladesh, but againts the other major teams i dont see him being effective. If god forbin Swann was to even get injured, England should always play 4-seamers - it would be a joke if they play 3 quicks + Tredwell in a test.
Graeme Swann's situation was different. Before he was recalled in 2007, after 8 years away from the national team. Was because he had improved significantly in domestic cricket. Swann was already the best domestic List A spin bowlers when he recalled vs Sri Lanka 07/08 - so his selection was based on performaces - rather than just him being "given a token chance".
Then after he impressed in ODIs, he was given a chance in tests & he basically just adapted to it beautifully & to date he has become a very solid off-spinner.