Hey painman80 - welcome to the forum. Judging by what you've posted, you're writing to the band members hoping for a reply. While this is the officially unofficial forum of DT and the band members do view the discussions on here, they (as far as I know) have yet to actually post on here.
As for your question regarding the 30th anniversary of the band, at this time, nothing has been said by any of them in interviews that they would do anything out of the ordinary for the upcoming tour. That's not to say that they won't, as they celebrated their 20th anniversary 10 years ago, and just celebrated the 20th and 15th anniversaries of Awake and SFaM respectively. So for now, we'll just have to sit tight and wait.
But as for inviting past members of the band to join them if they do an anniversary tour, I think that would be highly unlikely. Kevin Moore for many years has refused to make any comments about DT at all, and has refused previous invitations to join DT on stage (both in 2000 for the NYC show that was released as Live Scenes From New York, and for the 2004 show where they performed all of When Dream and Day Unite to celebrate it's 15th anniversary). And unfortunately, it appears that, aside from Jordan, MP does not currently have a good relationship with any members of DT. And with Derek being close friends with MP, I'd seriously question whether he'd be willing to join DT on stage or not. Charlie Dominici would be the only one I could see being openly willing to do it, and if he's the only previous member willing to do it, I doubt the band would have any past members join them.