Blizzard is always hiring....they just chose to highlight it, no big deal -.-
This. Blizzard is always hiring in multiple areas. Right before they announced connected realms there were a couple openings for network engineers. Did it mean connected realms (which we didn't even know about at the time) were going to be delayed when they posted those open positions?
And the fact that it's a lead position doesn't mean there's a problem. There's multiple "lead designers" for the coding side, they likely have multiple lead designers for the graphics side as well. This is probably an indication they're looking to add to the team. It is likely that a WoW artist could also be shared with Heroes of the Storm as well, since it appears the style of 3D modelling is going to be similar between the two games (they will certainly use the same tools to produce models for those two games).