Excellent news, Phelan is a very interesting, complex character and the dynamic with Todd is intriguing, I hope they continue with that like they started to touch on with Todd and Tony. Tony was a loss to the show, so it's good to have a replacement dodgy bad guy.
What would have been even more interesting is what Tony would have made of Phelan - probably would have seen straight through him but with a degree of admiration too. It's a shame we'll never know.
Still, if Phelan is sticking around, it makes the climax and aftermath of the flats scam a lot more interesting and unpredictable and perhaps the consequences much more intense for same of the characters involved.