It seems that Google is about to discontinue the Pixel 4a 5G just to replace it with Pixel 5a.
Apparently, the phone is no longer available on contract in the UK and in the US, it has vanished from Amazon and Best Buy. B&H Photo and Video shows the phone as being discontinued
The phone is still available on Google Store.
Although Pixel 4a 5G's disappearance from digital shelves in no way confirms that the phone will be discontinued soon, it does seem. Because the Pixel 5a could launch in late July or August.
If a report is any indication, Google has been affected by the global chip Shortage and it's also allegedly the reason why the Pixel 5a will only be released in two markets everywhere else the Pixel 4a might continue to be sold which came out in November 2020
You can check out my coverage on pixel 5a