They need to tone down their launch events unless they really do something new. People used to want to watch apple launch events live. The iphone launch will go down in history. The last notable launch I remember was when the retina macbook pro was launched, people were impressed- best screen ever and removing the optical drive was real news to talk about. Now apple puts on these events and there is no there there- they didn't add a feature android didn't have and their laptops probably won't have a feature that the xps or some other pc laptop already has. Maybe they'll surprise me with a real improvement in june and I'll get another mac.
I don't have hopes on more than incremental updates on some (not all) Macs.
Most likely, they will introduce an all new range retina MacBooks (14/16") w/o dGPU and slightly bigger screens maybe on cinema ratio.
And maybe they will announce an updated retina MacBook Pro 15.6 just getting current on Skylake and maybe Amd Polaris 11 GPU, lucky we could see a Xeon version and maybe an nVidia Quadro M GPU on such Xeon Macbook Pro.
About the Mac Pro, if updated beyond Xeon E5v4 and Thunderbolt, remains unclear it's GPU, options few for its TDP, maybe a pair of Polaris 10 and Polaris 10XT replacing D300 and D500, or an switch to nVidia Pascal GP104 or alike.
Mac mini maybe the only Mac with an real update or no update, since Intel Skylake actually it's cheaper on quad core that dual core LP it's very likely the quad core mini to return, also it's possible to include the powerful Intel skull canyon i7.
Less likely we could see an Retina Thunderbolt Display, I would be surprised if they decide to launch that one with dGPU on board, will do an perfect match on retina MacBooks and Mac mini.