I was told that Apple usually comes out with new laptops in September or October.
When it comes to Apple product releases, the only thing you can set your clock by is new iPhones every September - there will doubtless be a big "event" for that, the pundits always speculate about new Macs and they're always disappointed - the Sept. event is almost always about iPhone, Watch, Apple Music etc.
MacBook Pro launches
have often come later in Oct/Nov - and I wouldn't be shocked if the M4 MBP arrived then, but you really can't rely on it.
We're in an odd situation now because they've released M4 iPad Pros before M4 Macs which
suggests that we don't have long to wait for M4 Macs.
Currently, I wouldn't personally buy a M3 unless I needed to replace a dead or dying Mac - because it does sound like the M4s are coming Real Soon Now - but if you
need something then any M3-series Mac will be night and day better than a Quad i5.
Bear in mind the M3, M3 Pro and M3 Max variants are not
just about raw performance - odds are that a regular M3 (with 16GB) would do what you wanted performance-wise, but the pro & max offer progressively more maximum RAM, have more USB-C/Thunderbolt ports and support more external displays (the regular M3 is limited to one external display + the internal, or 2 external displays with the lid closed).