The assumption has to be inherent to your system. If this "binding tome" is a one-shot deal where you buy it once and your tomes remain through infinite TRs, its not beneficial to Turbine, like a permanent XP pot.
Its best if you had to buy said tome every time you TR if you wish to keep your inhenrent bonuses which will be great for Turbine if people TR more.
In the end, all we both have is speculation. I only run Hox, VoD, ToD etc for the tomes. +4 tomes can only become less rare in this scenario as more people get them which I think is a detriment to the long term.