Hit Em Up 2 already exists, I've got it. It's an unreleased track, and is a part 2 to the original Hit Em Up.
As far as having Eminem on the album, I don't think it's a tribute to him really. A tribute would be having Eminem produce maybe 1 or 2 songs, but not 98% of an entire album.
The reason people argue that Eminem and G-Unit and all them didn't know Tupac, therefore shouldn't be on a Tupac track, is because other artists that Tupac worked with and was close friends with, weren't even consulted about the albums or even considered. In fact, Tupac recorded the originals to the new songs WITH them on the track (Big Syke, Stretch, Snoop Dogg), and were cut off of the track in order to make room for new artists like 50 Cent and all them. Which to me, and about 90& of Tupac fans, is disgusting.
There was a petition on petitiononline.com a few weeks back, pleading to Tupac's estate to release the songs in their original form, the way Tupac meant them to be, or at least leave the original artists on the track and not warp what Tupac actually said (i.e, giving shout outs to eminem, replacement of verses, etc), and was the top petition on there for a while.
Having heard the new album myself, I can tell you that the beats aren't even on par with what Tupac's tracks should and have been. There's only a few songs on the album that actually have beats that match the theme of the lyrics. Pretty much all the other ones just suck. Although lyrics are the most important part, and the only thing I really pay attention to (especially with a Tupac tracK), it does help the mood of the lyrics when a beat matches what the artist is talking about. Eminem completely failed.