I own a Vega G2 as well as a Terminator Plus. I'm using a Sonore Signature Rendu SE into a Denafrips Gaia as my streamer for the T+.
I would not be concerned with the steamer becoming obsolete. I think every steamer on the market is software upgradable.
The Denafrips is a touch smoother with a deeper, wider soundstage, but the Auralic is no slouch. The Auralic is the more reliable steamer - never falters - while the Sonore has occasional pauses and sometimes just stops playing.
I bought the Auralic for my bedroom system because I wanted high quality but a minimum of boxes. The one big advantage of the Auralic is that it combines a built in preamp with a high quality relay-stepped-attenuator.
The Denafrips DACs have fairly high output impedance, so you will almost certainly need a preamp after the DAC. If you already have one (which I'm assuming you do), and don't mind the multiple boxes, then the Innuos + Pontus is probably the slightly better choice, particularly since you can further improve performance with a DDC.