It is not a good idea to give a short talk after every prayer without giving people a break; for by doing so people may be conditioned to think that it is integral part of salah. This has indeed happened in some communities in similar cases: Take for example the case of the collective du'a which some imams are in the habit of making after each and every salah, although it was not done by the Prophet, peace be upon him or the salaf al-ssalih (pious predecessors); nor was it prescribed in any of the four schools. It was introduced with a good intention in countries where people were new to Islam; thus they thought it would be hard on them to learn and retain du'as; so in order to facilitate their learning of transmitted du'as the practice of collective du'as after every prayer was introduced. Unfortunately, as the people have become used to it, they are often under the impression that it is integral part of salah; so many of them now seem to think that salah is incomplete without collective dua; thus they ended up distorting the very form of salah as transmitted by the Prophet, peace be upon him.
It is therefore advisable for imams to stay away from establishing such a precedent of giving a short talk after every salah; there is nothing wrong, however, in doing so occasionally. Let us never forget the Prophet's dictum, "Pray as you have seen me praying."