They could very well swarm again, depending on how the nectar flow is going in your area. You could try and remove the hive from the tree, but that is another post and topic all together. If you place, a swarm trap out you may catch one, try and give them what they are looking for. Place the trap 100+ ft away from the bee tree. If you can, put more than one trap out. Get them up 12 ft. or so above the ground with the entrance facing south-southeast. If you have any old drawn frames of comb that you can put into the traps this will help lure them to it. As mentioned before you can check into buying some swarm lures.
If you have the chance to see a swarm you can catch them very easy if you have a hive ready to go when you see them. Of course you can put a swarm in almost anything, but if you have a hive with frames all you have to do is shake them into the hive.
Yes if you bring in bees from another location, they will interbreed with each other. Now whether you think this is harming the bees that live in the tree that is your opinion and option. The honey bee (Apis Mellifera) is not native to north or south America. Most of what you see in bee yards consist of a mix. Unless they requeen every year from a well established queen breeder...and even then you can see some difference in the way the bees look from time to time.
I see that you are from Texas, so there is a chance that you have Africanized Honey Bees (AHB) in your area so bee careful.
BB
