Well what is done is done. You can expect some problems down the road but that can be expected in any tank. The sharks could become aggressive and take out most of the other fish and they may not, you never know. As for the pleco, he will get huge eventualy but not overfeeding and keeping his diet low will keep him small for a while. Make sure that your LFS or someone you know will take a huge pleco off your hands in trade for a smaller one down the road.
Another problem you might run into is making sure that everyone gets their share of food but sometimes that is the fun of having so many different types of fish.