so if i were to make talent points a reward i wouldnt have them instead of talent points in the next expansion. I would however have the new talents in 11.0 require all talent points from before 71 to be spent and any talent points gained between 10.0 lvl70 to 11.0 lvl71 be automatically granted. Make them part of the equivalent to the covenant campaign and in the final patch be almost immediately gained with alts having the points auto unlocked via skipping the story. This way you wont have to penalize players for playing the previous expansion by making their leveling experience feeling less rewarding AND you wont have to worry about players using those extra talent points to get ahead on the new talents.
Personally i would prefer them to not do anything with talent points and just give us unique effects on gear because i can tell you right now even just 3 extra talent points on some trees will lead to wonky builds that will need more balancing