No new airdrops planned as far as i know. In total devs have distributed almost 5 million SEM in 1.5 years and now it's block rewards only.
Recently devs have burned almost all premine including undistributed airdrop funds and major part of their own coins. So now there is only a budget for development and marketing left:
https://medium.com/semux/semux-foundation-burned-15m-sem-of-premine-4f34be96d3f0There is 380K SEM left in community distribution address. But devs said that this is not for airdrop, but for small bounties for contributors: copywriters, translators, active community members via discord tipping bot and other activities.