why he invited me then never followed up?

I had a great date with a guy recently - met him a few weeks ago. I thought the date went pretty well. I know everyone says people can be biased and think things are going well when they aren't, but I'm a very self-aware person and I generally have a good read on people date or not. I'm pretty confident when I say I think it went well, he had receptive body language (eye contact, asking me lots of questions about myself, he was definitely listening to what I said, etc). There was a lot of laughing and joking on both ends.

He made a lot of "next time we should..." comments, and also, after paying the bill (after I offered to pay my share), he said he had a lot of fun (I said I did too) and he asked if I'd be interested in joining him and his friends for a get together that upcoming weekend. I said yeah, sure! And he was like great, I'll be in touch with you soon with details, initiated a hug and then we went out separate ways.

The kicker is that I haven't heard from him in almost a week. If a guy was interested, wouldn't he have followed up by now? If he wasn't interested though, he could have just been more vague and said "see you around" instead of inviting me to something else - I would have gotten the hint. It seemed like things went so well the fact he didn't follow up at all is really throwing me off. I'd appreciate any opinions (guys especially!!) - why would he do that? I'm beginning to think he'll never call