I have up to 500,000 sku's to upload across 5 storefronts around the world. And then have these update daily for stock levels.
Sku's will be added 5,000 at a time.
How many products/sku's can Magento handle?
What is advantage to moving to 2.0 and how many products can that handle?
this is not about how many products you have,
it is about database size, sales/transactions per day and overall work in admin panel.
you have to go from there.
but products can be many more.
I have seen webshops with 1M+ SKUs so you should be OK with 500K.
Pick a good hosting solution plan.
You might have problems with reindexing taking too long.
For daily product data entry use MAGMI instead of default magento import functionality. MAGMI is insanely fast.