I saw the increase to 5%/5.5% too. It seems to be however only for the Bitcoin -> Monero trading pair. XMR -> BTC and also other pairs like BTC -> LTC are not affected.

I noticed that XMR reserves are usually quite low as this seems to be the most attractive trading pair (for quite obvious reasons). This might be the reason for the fee increase, maybe to get funds to purchase new XMR reserves?