For the moment no.

Mr. Sinister was a special man, which is to be expected of someone who was considered one of the most dangerous insane mad scientists in a world full of such people. As such, he didn't have friends, at least not in the normal sense; he had what he loosely had—those he considered equal but slightly below him. These were fellow mad scientists who had a lot of skill and no morality, which allowed them to work together on projects.

Those were the only group near him that could be considered friends in any real sense. The others in his life were either underlings of different kinds or rivals. Sinister is using his knowledge of mutants acquired over many unethical and deadly experiments to build his own personal mutant teams. The nasty boys were one, but over the years he had built several such teams for his own benefit.

The rivals he had were in the governments of the world. As a famous scientist of mutant biology, he had been recruited in several of the book's research projects. The scientists that were his partners on such projects typically did not want his help and so disliked his presence in whatever project they were supposed to be in charge of.

Then another group connected sinisterly with the corporations. As Mr. Sinister, of course, being of rather dubious character, had, of course, used his scientific talents and research to start up several genetic corporations. They were more fronts for his dark projects than an actual corporation, though he did make sure they brought in a steady flow of cash to help fund all his research.

One other group that were diverse in their thoughts and feelings on Mr. Sinister were his chimera projects. Those who had been born in his labs from mixing the DNA of two different mutants, causing the new mutant to have both their powers; hence, these creations of his were called chimeras.

The last but most important group involved with Mr. Sinister was clones. As he had put quite the target on his back with his actions over the years. So as a contingency, he had created many coobes to take his place when he was supposed to die. Also among the clones were the four special ones. Each is a distinct variant of himself meant to continue expanding his research in new ways.

These special clones were marked with card symbols. So there was Diamond, Club, Spade, and Heart, each of them intelligent and ruthless in their pursuit of whatever research they were focusing on. So of these groups, who are the most likely to come after Phoenix and Mr. Doe?

None at the moment. As with Mr. Sinister having so many clones acting as body doubles, it will be a long time before anyone notices his ****, if they ever do. Not to mention they're far more likely to carve out chunks of his criminal mutant empire than her **** for him.

Though that doesn't mean there isn't any future danger that these allies of the dead Mr. Sinister might pose. As the body doubles might try and finish what the original started just to prove that they are the true Mr. Sinister. Some of the chimeras might see themselves as his children and try to avenge their father, though that is unlikely.

One of the four special clones might gain interest for whatever reason in Dr. Doe or Phoenix. It is even possible one of the teams of mutants might want **** for destroying the destruction of the cash flow. These reasons and more besides may bring future trouble upon Mr. Doe in the future, but not immediately, and they all might still never know the original Mr. Sinister is dead.

So while the present is secure, the future is certainly not. That is to be expected in a world of mutants, aliens, and sorcerers that bend reality on a daily basis. It's not all that surprising all the trouble one dead supervillain might cause, especially one such as Mr. Sinister. Though only time will tell if any of these relationships of Mr. Sinister may bring danger to Dr. Doe and his new home.