While most of the time we will suggest a minimum of one year for a lease, there are certain circumstances in which we will suggest a shorter one. This may very well be one of them. If the difference is only a month or so, then you may not want to bother, but if their lease is not up until October and it is only May or June, you may want to look into finding a temporary resident for the time being. This is perfectly fine if you do need the money from your rental property but really really want that other resident.
The only thing that we suggest is that you make it very clear from the beginning that this is strictly a temporary arrangement. Let your temporary resident know that they will not be able to renew the lease past a certain date and that you will need time between when they leave and when you rent to the other people. Make sure that your preferred tenants know this as well so they aren't surprised if they find small marks on the wall or smell fresh paint even though you said you had done it a few months before.
Having a temporary vacancy can be a bit of a headache for landlords, but there are ways to make the best out of it. You may even want to give a discounted rate to those who are filling the rental for the time since they will have to find another place so quickly. Whatever you decide, just remember to be open with your tenants. You certainly don't want any miscommunication between yourself and people that will be living in a building that you own.