It is a lot of speculation, but it would explain how Nokia intends to bring Qt to low-end devices: using linux.
Qt for Symbian still has a lot of rough edges, and judging from that experience a lot of people (including myself), don't believe Nokia would be able to bring Qt to series 40 or any other new OS in a reasonable amount of time, in a good working state.
But if they intend to use a linux distribution as a base, that would be a totally different situation. Or nokia intends to use a similar strategy as in the N900, a device that is effectively an internet tablet + Series 40 phone glued together. All interesting speculation, let us wait and see.