Is it worth starting now?

The title is kinda wrong, because i started on day 1 but i stopped playing because of real life stuff. Now i am coming back but i am not sure if it's worth it. Will everyone be farming current content? Are T4 raids still being run? Will i be able to get a raid spot? I have no experience with tbc prior to this so i dont know how things work. I also have a rather limited expereince with raiding as well.

By far most people aren't doing T5 yet. Kara pugs are rare. There are a lot of normals and Heroics being run and people are busy gearing up for raids, so yeah, it's definitely worth starting now. When you hit 70 you won't be surrounded by T5 geared people.

still lot of stuff going on :)

you missed nothing. barely t5 is out enjoy yourselve mate :)