When the Democratic Presidents stop being neoliberals only out for themselves. Before 1994, the Democrats had the House for 40 years straight, and 60 of the last 64. Since then they've had it for only 4 out of 24.
I don't quite understand how you are making this connection. There are numerous reasons why Democrats should move left and stop pandering to corporations and the wealthy, but Democrats moving right in the late 80s+ is not the reason they lost their generational hold on Congress. Why that happened is not that simple, and Democrats were probably going to lose Congress anyway. Not everyone at the time thought Democrats had all the answers, and appreciation for concepts/positions brought to dominance by the New Deal had worn off with newer generations by the time the 80s came around. Otherwise you would not have had Republicans running roughshod over Democrats with the concept of more limited government.
Thoughts and ideas embraced by one generation may not be by the next. Substantially mitigating the issue of consolidated corporate power and income inequality may result in those issues becoming less important to newer generations of voters who have no appreciation of their seriously negative effects, and thus begins a cycle of their renewal as we can see in this era.