Brin also sets up future story-lines, there are hints that Daneel is slightly outwitted by his enemies and that either the Seldon we see at the end of the book is a clone/robot or they have a clone/robot of him - what else to make of the sequence where Seldon notices that the rejuv machine they put him in has another chamber which seems to contain another body? That is the logical fit I think (unless I missed something?) and allows seldon to travel 500 years into the future without the time machine *and* still be officially dead.
Have you read Brin's epilogue? He intended payoff to that
, but then cut it.
Personally, I think it's a Ganger Seldon we see in the third act of Triumph
. I'm not quite sure where the switch was made, however.