1. Shocklands will be reprinted: 87%
There's a lot of circumstantial evidence pointing this way, and I think it's highly likely. Look at M13. Farseek over Rampant Growth? Arbor Elf over Llanowar Elves? Mutilate? Etc. There's like a bazillion cards that synergize with basic land types and it's extremely conspicuous. Zac Hill even did the whole Nudge Nudge Wink Wink deal when he previewed Liliana of the Dark Realms, and he said the M10 duals were reprinted because of how well they worked with RTR. Well of course dual lands work well with a multicolor set, but any other dual lands would have worked fine too, right? Why these ones specifically? Oh, look, they care about basic land types, hmm. Either Return to Ravnica is going to have nonbasic lands with basic land types, or Zac Hill is the world's biggest troll.
Furthermore, it's no secret that they're actively looking for places to reprint Modern staples to keep the format accessible and such. Shocklands are the epitome of Modern staples. Shocklands are also one of the things players remember fondly from the first Ravnica block. But even if you discount the nostalgia factor, a set of powerful dual lands still fits into the block for the same reasons they fit so well the first time around: powerful manafixing is necessary to promote a heavy-multicolor environment.
Mark Rosewater--who is on the Return to Ravnica design team--is also on the record as saying he is happy with their design, calling them "probably my personal best design for dual lands". This doesn't confirm anything, but it should dispel any worries that the shocklands might have fallen out of favor with R&D.
Now, on the other hand, there's still a chance that they make new lands with basic land types rather than reprinting the shocklands. For example, maybe they want to call back to the original Ravnica block, but they also want to mix things up a little and give the players something new instead of repeating the old.
Uh...I don't find that super-convincing. I'll concede that it's possible, but given that we know they want to find places to reprint Modern staples, I think it's unlikely.
2. There will be a blue-red card with the type line "Planeswalker - Jace": 57%
I think this is a reasonable line of speculation. The evidence for it goes more or less like this:
- Gideon Jura is confirmed as Boros-aligned in Gatecrash.
- The tagline for Return to Ravnica is "Choose your guild."
- Gideon chose a guild.
- Therefore, all the other planeswalkers in this block will choose guilds too.
- Jace Beleren appears in promotional art for the set.
- Therefore, Jace will appear in the set as a card.
- Therefore, Jace will choose a guild.
- Jace Beleren appears in promotional art next to Niv-Mizzet, leader of the Izzet (a blue-red guild).
- Therefore, Jace will be Izzet-aligned and appear in the set as a blue-red card.
Odds of there being a Jace card in RTR: 99%.
Odds that Jace, story-wise, will be on the Izzet team: 75%.
Odds that Jace will be a blue-red multicolor card: 55%