Hey there,
This is a great question and a common one. Let me provide some insight.
mappleby
Lots of applications have a question somewhere asking if you are "sponsored" by your employer. That is what you are looking for. I have no idea if it actually helps unless you are applying to one year programs or something like Columbia's J-term where there are no internships.
This is a valid place to enter this information IF you are being sponsored. Forgive me if I'm wrong, but it seems OP isn't sponsored, merely guaranteed a position upon return. Additionally, if you're being reimbursed upon return, you shouldn't enter this information here. Sponsored means you have tuition assistance coming in. Reimbursed means you'll only get that money if you come back. This can have implications when it comes to financial aid potentially.
NeanderthalMan
I'm certainly not an expert. If you volunteer that your current employer is going to give you your current, pre-MBA position, two years from now, it seems the natural follow up is, "Then, why get an MBA?" When describing your post-graduation goals, it doesn't sound very inspiring or aspirational to say, "I'm going to take my old job back." Now, you may have an excellent response to such a question. Without a compelling reason, such as returning to and eventually taking over a family business, I think I wouldn't mention it unless pressed on what I might do if my post-graduation goals didn't pan out.
You have a valid point for some instances. A lot of people run into issues where their return offer flies in the face of their stated short or long term goals. However, I think there are many situations in which you can make a strong case for an MBA even if you are coming back. This is really a case by case basis. Even if it isn't your short or long term goal, you can definitely mention it in an interview - it speaks to your caliber so that's always a good thing.
As for the concern schools have about you after you graduate, most of the top programs run at 85 - 90% 3 months out so unless your short term goal is something that could really have you couch surfing, they are probably not too concerned.
I hope that helps!
Bhavik