I got a master's degree from the US in 2013 and received H1B approval this year 2014. However, I am thinking of doing my MBA next year (2015). If I apply for a F1 visa again next year, can my future employers sponsor me (after I graduate in anothe...
I assume a cap subject H-1b petition was filed for you, and approved for an October 1 start date.
If that is the case, and you begin working on October 1st when your status changes from F-1 to H-1b, then you could change back to F-1 (with a new I-20, and either a change of status application, or a new entry with an F-1 visa). When you finish your program, an employer could file an H-1b petition for you based on your new degree, with an appropriate job offer. You would not be subject to the cap, if the new petition is filed within six years.
There are good reasons to take advantage of a new period of OPT should it be available when you graduate your new program before changing to H-1b again.
Keep in mind that if a petition was filed for you to change from F-1 to H-1b, the approval of that petition does not give you a "visa" - only a status. To enter the US in H-1b status, assuming you are not Canadian, you will need an H-1b visa issued by a US consul. But if you do have an H-1b visa, and it has not expired, you can use the existing H-1b with a new petition approval - even though the visa is endorsed for a different employer.