As part of its unveiling of iOS 15, Apple (AAPL) said users of other operating systems will be able to join FaceTime calls when invited via a link sent by an Apple user. 

The announcement about FaceTime was among a slew of other software updates introduced for the iPhone, iPad, and other Apple (AAPL) products. The move to allow non-Apple customers access to one of its apps is unusual for the iPhone maker, leaving some to wonder whether access to other popular Apple software products might be expanded, too. Part of Apple’s appeal has long been exclusivity — you have to buy the company’s gadgets to get access to its high-quality software, and vice versa. But the FaceTime decision appears to be an acknowledgment by Apple that there are competitive benefits to letting non-Apple customers use its software products, according to industry analysts.

But there are still limits to how far Apple may go in the direction of openness —limits perhaps best exemplified by another one of the company’s apps, iMessage. iMessage is beloved by iPhone users thanks to its wide range of features that go beyond traditional SMS messaging, including the ability to react to text messages and to see when your friends are typing. The app also uses end-to-end encryption so there is no way for Apple, or anyone else, to view users’ conversations.

Recently, Google has tried to replicate some iMessage features, suggesting that many Android users — who far outnumber iPhone users globally — would be all too eager to gain access to Apple’s little blue text bubbles. And yet, for the most part, analysts say Android users shouldn’t hold their breath for a non-Apple version of iMessage, both because of the competitive landscape and the power of iMessage in selling Apple products.

Apple does still face competition to iMessage, not just from Google but also increasingly from Facebook-owned WhatsApp. Apple has been working to make iMessage more closely mirror social media platforms to better compete with WhatsApp. But WhatsApp still has one major leg up on iMessage: It’s available across a range of devices, making it a default choice for people who want to communicate across operating systems.

Just as Apple’s decision to wait more than a year into the pandemic to expand FaceTime access may have caused it to miss out on the opportunity to become the platform of choice for virtual family dinners and work meetings, keeping iMessage as an iPhone-only software risks keeping it from becoming a default cross-device messaging app.