No.
As you pointed out it is still being well supported. With an install base of 138million it is a very popular brand, Sony would risk alienating people from the Sony Playstation brand if it was to drop the PS2.
I don't see it as any kind of hindrance to the PS3; I see it as supporting the PS3 by still allowing access to the Playstation brand to a wider audience. It's not like the PS2 is a direct competitor to the PS3 as they don't receive the same games, the PS3 has online functionality, they have a wide price disparity, they are not the same generation and the PS2 lacks dozens of features available in the PS3.
If people wanted a current gen console they would buy a current gen console. If people want a PS3, they wouldn't buy a PS2.