I am going to continue to read fanfiction with Ianto/Jack (to help me feel better) but I am definitely done with the series with this ending.
If there is a series 4 the only way I would watch it would be if they brought Ianto back and I don't see that happening at all. I will not watch a show with Jack (if he comes back) and Gwen along with a new cast alone because to me the show was Jack and Ianto since I lost Owen and Tosh the season before. I have always thought Gwen was the worst character on TW and she ends up with the happy ending

Good bye Ianto, Tosh and Owen...You were the best things about Torchwood and now there is nothing.