Why would anyone spend huge money on pipes if there won't be enough stuff to pump trough?
There may still be some gain to be had from Western technology, since, as is noted here Halliburton and Schlumberger are using horizontal drilling, hydrofracing and other EOR techniques to improve old field production and this potential is also addressed in references to Dave's excellent review of the current Russian situation, by field.  
Russia is railing large amounts of oil into China now (and China rails them further into their refineries).

Pipelines are MUCH cheaper (and more energy efficient) ways to move oil in quantity.  In the US very little oil is railed, almost all is either pipelined or shipped via water (also more efficient than rail).

Since Russia will be producing large (if some what smaller) quantities of oil for many years to come, the capital investment in a pipeline may well make sense.

Chinese rail lines are well (and sometimes over) used today.  Taking oil off of them would free up space for goods that are trucked today, reducing Chinese oil consumption.  The Chinese seem to be quite serious about not growing their oil consumption too much.

IMHO, China wants the pipeline more than Russia does.

In 2004 Russian oil exports to china was about 6.5m tonnes, or 140,000 boepd. This is doable by rail.

IMO China would want to source more from Russia. And if Russia could up its production in the East, why not sell it to China. On the other hand it might be easier to ship it by sea form Eastern Russia...