Today, the FSOL and FSOLDigital Facebook pages showed an image with six CD covers, and the caption "THE ENVIRONMENT SERIES. Now available on FSOLDigital.com". The six cover is that of one of the inner booklet pages of Environments 2, suggesting that it might simply be there to add symmetry to the image. It's also possibly there to suggest that a sixth is on the way. Not that past teasers have meant imminent release (volumes three, four and five have all been mentioned two years before their actual release) but with the initial rumours of Five being a double album, and the lack of tracks such as the previously heard '******' and 'Strange Glare', there is always the possibility that Six might be here soon.
Or it could just be for symmetry purposes.
Check out the image and join the speculation here.