I think they will use the same things they do now, but maybe with more advanced technology. I think people are going to keep using text messages and email. I think those are dominant forms of communication because they work well. The future might be a bit more high tech though. I definitely see people using a lot more video calls in the future. The advent of Skype is a good example of that. You used to have to pay for video calling, but now it's free and easy to use on just about any device you have.
I also see social media being a huge part of our lives in the future. People already use Facebook and Twitter constantly, so it may become even bigger than it already is. Social media is a great way for people to share information quickly and easily. It has its drawbacks, but the advantages outweigh them for most people.