A recent Netflix shareholder letter and an interview with GigaOM (link) makes it clear that Netflix is evaluating different tiered pricing plans.

On page 2 of the shareholder letter (link) , the CEO explains:

"Last April we introduced a 4-concurrent stream $11.99 option to begin our evaluation of plan tiering. Since late last year, we have also been testing 1-stream and 3-stream variants, as well as SD/HD variations, at various price points. Eventually, we hope to be able to offer new members a selection of three simple options to fit everyone’s taste. "

There is no need to panic as Netflix will take care of existing customers when they make the switch and they also state that no final decisions have been made on how and when this will change. 

Hastings did clarify that the tiered pricing will not be for access to content but rather for value added services (such as multiple simultaneous streams).