Even the iPad Air 2, which was a nice improvement on the already solid iPad Air, wasn't enough to stop Apple's (NASDAQ: AAPL) iPad sales from crumbling over the last several quarters. To be sure, the iPad still brings in billions in revenue per quarter for the company, but Apple must halt the decline in iPad sales and, eventually, get the product category growing again.

In light of this, I believe Apple needs to bring Force Touch, which is expected to arrive with this year's iPhone update, to the iPad Air 3 due later this year.

Why Apple normally wouldn't bring Force Touch to this year's iPad
In a conversation with fellow Fool and resident Apple guru Evan Niu about the possibility of Apple bringing Force Touch to the next-generation iPad, he suggested it might not happen this year. Here's his reasoning:

Apple tends to bring new features and technologies to the iPhone first before the iPad, since they're generally easier to implement on a smaller device. Naturally, the iPhone is such a massive part of the business that it also deserves the highest priority.

It's hard to disagree with this logic. Apple has, indeed, used the iPhone as the vehicle to introduce its newest and best technologies. Remember how Apple made a big deal at the iPad Air 2 launch about how it was now optically bonding the cover glass to the display? Well, this had been standard on iPhones (and, according to DisplayMate's Raymond Soneira, several competing high-end tablets) for years.

Another well-known example of Apple bringing innovation to the iPhone first is Touch ID, which made its debut in the iPhone 5s in late 2013. It didn't show up on the iPad until a year later, with the iPad Air 2/iPad Mini 3.

Under normal circumstances, I would wholeheartedly agree with Niu. That said, in light of the relatively poor financial performance of the iPad business, I think Apple would benefit from introducing Force Touch on the next flagship iPad.

Force Touch is a big deal that could drive upgrades
The popular hypothesis for flailing iPad sales is simple: people are hanging on to their iPads for quite a long time. Apple's latest iOS 9 update, which should roll out to customers this fall, should help convince people to upgrade by virtue of the fact that one of its key features -- split-screen multitasking, or "split view" in Apple marketing parlance -- will be exclusive to the iPad Air 2 .

That's a nice one-time thing, but to sustain the momentum and to keep customers interested in upgrading to the "next big thing," Apple must introduce such "exciting" user experience features every year.

Imagine if Apple were to release the iPad Air 3 that only offered a faster processor and a better display. Some folks (including yours truly) would find such a device exciting, but I suspect those upgrades alone wouldn't be enough for the vast majority of customers.

However, if Apple were to introduce an iPad Air 3 with Force Touch, as well as a suite of in-house apps that take advantage of the technology, then not only might such functionality compel users of older iPads to upgrade, but they would be more likely to upgrade to the latest iPad instead of a price-reduced iPad Air 2.