Gates are of a cycle of dual lands coming out in Return to Ravnica. There's a gate for each guild (WU, BG, UR, BR, GW), but they always enter the battlefield tapped. These are in stark contrast to the shock lands that reappear in this set (which only enter tapped if you do not pay 2 life), the duals from the core set (which only enter tapped if you do not already have, for example, a swamp or mountain for the dual that taps for R or B (ironically, the gates would allow this to not come in tapped)), and lands from previous sets that came in tapped only you already have a few lands. The Innstrad lands work the same way, even though they aren't always aligned with the guild colors (They have BW, not WU. But they do have BG and UR, very nice.)
So that's the background. Is the entering the battlefield tapped going to be too slow? You're basically sacrificing whatever turn you're at to be turn - 1, which is a pretty hefty price to pay (apparently, it's worth 2 life!) Are these only going to see play in limited to facilitate mana fixing that otherwise isn't available?