Ok so in the last episode we saw Iris die but there is still a way they can save her and stop Savitar. In the rare possibility that this theory turns out to be true, leave now if you don't want it spoiled or want to go into the finale without expecting this ending.

The point of Savitar killing Iris is to have Barry travel back in time to save her, thus creating time remenants one of which is Savitar. So if Barry wants to save Iris, this is what he could do.

He could travel back to the moment before she died, open up the time portal just behind Savitar, punch him over, grab Iris and throw her through a breach created by Cisco which lands her inside ARGUS.

If Iris is inside ARGUS she is safe because of the power dampener used by the building. Then Barry works with the other time remenants to defeat Savitar in a fight. What they do with Savitar after he is beaten I have no idea but what happens next is the main point.

After saving Iris, the Speed Force will be angry that Barry has changed the timeline once again and will want to take him just like they did Hunter Zolomon, but there are two Barry's, the Original and the one who is meant to become Savitar. I personally believe that by saving Iris, the timeline is completely changed and TR Barry will sacrifice himself to the Speedforce to save the Original Barry and prevent Savitar from existing.

If this actually happens the timeline will be screwed once again and will trigger the cliffhanger for season 4.