The answer is: No. The maintenance call for Orders that are already created had a status "Called" at the item level. So if you had e.g. 2 Items and they have been converted into 2 Work Orders this month, and you now add a 3rd Item, no new Order will be generated for this month.However, you will get 3 Work Orders the next time the call is due.
N.B. Is this a Single Cycle plan? It may be a bit more involved with Strategy based plans, since by adding new Items you might very well add new relevant Packages to the schedule, and you might also need to consider that the new item will start in the cycle as well.