You can if:
You rename the .capx to .zip
Extract it and then open the extracted .caproj with notepad
Change the line near the top that reads '<saved-with-version>TypeNewVersionHere</saved-with-version>' to whichever version you want and save it.
You can then just open the .caproj directly, or zip it back up and rename it to a .capx.
I guess it might not work particular well if the capx includes new features though!