Best guess with the available information at hand.
Israel has been doing a lot of fighting the West Bank recently. Israel has also warned that they will go into Gaza should they deem it necessary for self defense. If fighting breaks out in either or both regions, more troops will be necessary.
Fog of war at this time is limiting, but the call up is a warning indicator that something bigger may be afoot.
Thanks... my guess too, but you have facts to back up your position.