Devaluation simply means you get less for your Avios. Avios is a currency of sorts, paid for with hard currency, and the risk of devaluation - or if you prefer "inflationary pressures" - means your pool of Avios could one day be worth less than today. There are two main ways it could happen - either making Avios more difficult to earn, which seemingly never happens, if anything the opposite; alternatively you need more Avios to do whatever it is you are planning. There is a variant, which is probably the more likely scenario: restructuring and changing the programme such that some things are cheaper, others are more expensive. The last change did this in that UuA become more expensive and shorthaul domestic add-ons were removed (both were close to being too good to be true) but off peak redemptions meant many point to point redemptions needed fewer Avios. Either way, it's like having a pile of cash in a non interest earning bank account, which may make sense in the short and perhaps medium term, but unlikely so in the longer term.

I have no specific news in this area and when BA last did this there was a window of opportunity to deploy Avios before the changes came in.