Assets from other platforms will be able to migrate to the Waves blockchain. From NXT, Ethereum or other platforms(at start by burning supply and issuing it next on the Waves blockchain).
Later, implemention of crosschain asset protocol will follow to enable two-way communication between different blockchains.
You will be able to issue your assets on the Waves platform and burn the ones you have on your existing blockchains if you only wish and if it is a legit project/asset.
Waves will have its own decentralized exchange.
what's the most obvious difference between waves and lisk.
Building first production system on top of Scorex framework where Waves token will be the fuel of whole platform and all transactions happening there, from issuing the assets, through transfer, depositing and withdrawing other supported currencies on the platform. Focus on custom asset creation, decentralized exchange, asset-asset trading, fiat assets, working with payment providers from the start and being decentralized kickstarter at the same time.