Intalio lets you attach an interrupter timer to a sub-process(group of task in the process flow). When that timer is hit (48 hours in your case) execution jumps out of the sub-process to the next task in line. I think this might be exactly what you are looking for.
Human interaction tasks (like completing a form) also have a deadline option that you can set in the mapper. When the deadline is hit the human interaction task is canceled and the process automatically moves on.
Edit. Added a picture to show how it looks in Intalio designer. When timer is hit process moves on to Task 3. You can also execute a separate stream (optional task in this example)
https://i.stack.imgur.com/2AmrN.png
Hope this helps. Cheers.