Unless they either have some seriously insansely popular exclusives and/or undercut Steam on prices (assuming a similar range of titles), then no. Steam has been around too long, is more advanced, mature and developed, is proven and established with a larger library and most users who use digital delivery to date choose it. It's a case of too little too late. They may get some customers, but the lion's share is spoken for.
If they can undercut on price however, and/or offer exclusive must-have titles they can draw some customers based on those things. But I'd probably prefer to buy those must-haves in a box rather than a non-Steam DDP.