Will houses unite with Slytherin?

[Mint]

We heard the sorting hat - 4 houses Must unite for this battle!!!
And it seems that though Dumbledore's Army - houses did unite....3 of the houses that is. How will they even make SLytherin part of the union? Will they be able too?

There are couple of problems with SLytherin. There are children of deatheaters there. We dont know how many of them are in Hogwarts (we know that they all would be in SLytherin, no?) MAy be majority of SLytherin are deatheaters. With that in mind how can anyone from that house be trusted not to be a spy for their parents?

And other Slytherins are seem to be not welcomed by other 3 houses. I am sure that not all of them are bad kids, but they do have great deal of pride. If Slytherins were rejected by kids the first time they wanted to be friends - they will probably refuse to do it again.

[choki]

I suppose Slytherin will join force with the rest of the houses and fight united as Hogwarts' students not as individuals.
There might be some spies around, but I presume most of the Slytherins aren't that dark/evil except for Draco and his gang.
Well, people changes as they grow up, by that time they will be 17...they will have to decide to follow their fathers' footstep or to walk their own path of righteous

[Mint]

Yes, they will grow up - but what will they grow up as? I mean, that the whole point of the other houses not liking SLytherin - a lot of kids in there grow up to be power-hungry evil adults! I mean take any evil witch or wizard - and we all immediately say that they are from SLytherin.

Has anyone ever considered that Umbridge was in Ravenclaw? Or Hufflepuf, or gryffindore? No - because of her evil nature we all say that she is in SLytherin. ANd if we are right - then perhaps majority of the house will be against uniting. Im sure couple of people from there will join DD ARMY but they need more then couple of people - they need a majority of the house to really form a union.

I think there will be some sort of shocking event that will make them all join together. But what can this event be?