Well, if you've got a long TBR list, then probably by the time you've actually read the book, the sequel will have been out long enough that the TPB will have been released and the e-book price thus dropped and you'll be pondering whether to spend the money on the brand-new 3rd or 4th in the series.
Win-win!
BTW, Bloomsbury is non-Agency so it'll be couponable at Kobo and Borders and Amazon is free to set whatever price they want, so it might be worth it to put the title on pricedrop alert over at eReaderIQ or wherever.