Kinda.
The Core books always sell best, this is true. However, this is also because they're the books everyone buys first. So they should always be in print and available on shelves; the core books should generate a continual profit year after year.
This is something WotC is currently struggling with, as they seem to have a MtG mentality for D&D, where you have to continually have a new set each year, and past products are immediately forgotten. It's actually better to have a video console mentality where the console always has to be one sale and continually generates better and better profit while you sell accessories for that central product. Paizo has this, where each year they sell more Core Rulebooks than the previous year. That should be the focus.
Once again, I don't think you can compare Paizo's and WotC's situations. They are not at all similar based upon the amount of money the two lines are expected to generate from fiscal year to fiscal year.
If Paizo is able to generate a stable level of sales each and every fiscal year based primarily from their accessory line subscription service-- say they generate $500K each year (picking an arbitrary number just as an example) they're good. They can ride that $500K for as long as possible.
But WotC's core rulebooks for a new edition are SO frontloaded in sales and generate so much money overall (compared to the rest of the RPG line)... that it throws their yearly ledgers completely off. They THINK they have a huge game on their hands based on Year One sales (and start trying to plan their lines with that idea in mind)... but then they realize that's not necessarily the case in Year 2, Year 3, etc. etc. So if WotC generates $10 million in Year One (almost entirely from the frontloaded sales of a new set of core books)... then in Year 2 generates $5 million from their accessories and support products, then $2 million in Year 3, $1 million in Year 4... that kind of fluctuation is unwanted in a corporate environment. It's the same reason why Morrus said (back when he first offered up the ENWorld subscription service to people) that he was only doing monthly subscriptions, and not have a "pay once for the year" option. Because it's much more difficult to plan and organize your year-to-year and month-to-month finances when you don't have that kind of consistency. Heck, that's why DDI was so important to WotC too... because they always knew each month they had X number of dollars coming in.
That's WotC's big problem (and why I don't think you can compare them to Paizo.) As weird as it is to say... a new edition for them is just
too popular. Too much windfall at the top and not enough in subsequent fiscal years. Heck, truth be told, I wouldn't be surprised if WotC would actually prefer (if they could get away with it) to release a new edition of D&D
every year, just to get the same level of base sales year-to-year from those core books, even if overall it ends up generating less money total than a single line that suffers diminishing returns. If given the choice between:
$10 mill / $5 mill / $ 2 mill / $1 mill / $500K (Years 1 to 5 of one line - $18.5 million total)
versus
$3 mill / $3 mill / $3 mill / $3 mill / $3 mill (new line each year - $15 million total)
Most companies I think would prefer the second option.