Rumors have been swirling about Apple working on an iPad that falls inbetween the 9.7" and 12.9" sizes they currently offer in the Pro lineup. John Gruber and Jim Dalrymple briefly discussed this on the latest episode of The Talk Show, with Gruber saying: “It doesn’t make any sense to me.” (discussion at 1 hour 41 minute mark). There is, I believe, one explanation that makes too much sense not to be true.
His numbers check out. An iPad with the same footprint of the 9.7" iPad Pro but a bigger display with the same pixel density of the iPad mini sounds like a very compelling iPad to me.