They did release Ashes of the Singularity, which is a large scale rts, with special dreadnoughts that level up. (I think one of the stand out features of Sins is the customizable cap ships.) I guess a big part of it is what counts as a "4X rts"? If it's any large scale rts then you've got the Total Annihilation lineage, including the beloved Supreme Commander. Paradox does make real time games that focus on empire building, but they're markedly different from what I've heard; you don't control individual units in battle, instead grouping them into a fleet, smashing them into an enemy fleet, then dice roll and modifiers are applied and a few minutes later it says "We've had a decisive victory, and three carriers were damaged." You may like them if you want more empire building and politics, but they aren't for in depth battles.