It should be gems, gems would change everything. Kudos to Marvel Studios for planning their lineup of films. (“Captain America: Civil War†will cross the one-billion mark.) In case you haven't figured it out, the Marvel superheroes and villains are drawn together by the Infinity Stones. In case you lost track of it, let's do a recap.
The Space Stone, which made its first appearance in 'Captain America: The First Avenger", was last seen in Asgard. You would assume that it was safe until you recalled the last scene in "Thor: The Dark World". Loki was impersonating Odin. (Yikes!) The Yellow Stone would be easy to guess. (You haven't seen "Captain America: Civil War" if you don't know the answer.) The Reality Stone, which almost put an end to human civilization, ended up in the hands of the Collector. It was hard to tell if he would use it for personal gain. As for the Power Stone, the Nova Corps kept it for safety. Ronan the Accuser could have used it for further destruction, but Star-Lord find the way to distract him. (This was one of those instances when an awful singing voice and bad dance moves could save the universe.) This would leave the Soul Stone and Time Stone.
If you've been reading too many online reports on the upcoming Marvel pictures, then you would know that Chris Hemsworth was guaranteed an appearance in "Avengers: Infinity War". This was rather a case of bad reporting, as Thor left the Avengers Headquarters (in "Avengers: Age of Ultron") to unlock the mystery behind the Infinity Gems. But it's not a case with Star-Lord and his ragtag team. (A meeting with Thanos would be a possibility, as there won't be such a thing as a wide universe.) As for the other questions, let's answer it. One by one. Pay attention:
Will Doctor Strange appear in "Avengers: Infinity War"? Yes. At this point, no one can tell what film will the Soul Stone makes it first appearance. It has the ability to manipulate both living and dead souls, so it's not hard to guess that Doctor Strange will be drawn to it. But a villain will be interested in it too. As for his (or her) identity, we have to wait until November 4.
Will the Fantastic Four join forces with the Avengers? Sadly, no. Any hardcore Marvel comic fan will tell you that the quartet, and the Silver Surfer, play key roles in vanquishing Thanos and making sure that the Infinity Stones won't be in his possession. The reboot of "Fantastic Four" was a bomb, but 20th Century Fox don't have any intention of transferring the rights to Marvel Studios. Perhaps less will be better.
Will Magneto have a cameo appearance in "Avengers: Infinity War"? You wish. "X-Men: Apocalypse" would reveal Erik Lehnsherr and Peter Maximoff to be father and son. This means Wanda, Peter's twin sister, is Erik's daughter. Alas, Peter was killed in "Avengers: Age of Ultron". Fox producers aren't looking at the bigger picture. Win some, lose some.
Are there other superheroes appearing in "Avengers: Infinity War"? There are rumors about Frank Castle joining the gang in the first part of "Avengers: Infinity War". (In case you don't have any idea, Lions Gate Entertainment released a live action feature of "The Punisher" in 2004. Tom Jane played Frank Castle. It was a box-office disaster.) Fans can confirm it next year. (Production might start earlier.) As for Captain Marvel, he will have his own film three years from now. No word on who will play this superhero, but fans relish his fight with Superman. It will be nice if Warner Bros. allow Henry Cavill to do a crossover.
Who owns the Time Stone? As its name implies, the Time Stone has the ability to control the past, present, and future. It will be safe to bet that it will make its first appearance in the first part of "Avengers: Infinity War". Maybe Thanos has it all this time.