I can see a huge decline in Dbones RuneScape Gold. I'll say soon they might go as low as 2K. In the longer term maybe even more than 2k. Prayer is among those abilities that are highly dependent on updates to keep growing in value. For instance, Piety is available, and prices rocket with 1000 gold rising overnight.

Why? There's a lack of bones in circulation, everyone would like them, but supply is drained and prices skyrocket in order to compensate. As long as there's not any new information released which makes high prayer essential, it will fall steadily. When you start to see new prayer materials that call for a higher amount of prayer (70-99) then it'll increase in the future.

However, if there's no update the number of users will continue to decline. Maybe not too much every week, but it will gradually decrease a little each month as years go by. It's just a volatile skill which is similar to herb-based lore. The bots of frost dragons having in a ball, and blue/green dragons overflowing with bots I can see the cost going down RAPIDLY.

Some might argue that prayer is a money-loser... literally and certainly. If you're able to, say, 95 prayer and experience chaos, you pk and deal with it and soon start making more money then before. Thus, praying can make your money indirectly. Price will fluctuate up and down in a day but it will continue to go down in the future.

Runecrafting: It's likely to take the longest time, in general, you'll need to ZMI if you have access the lunar spellbook. Alternately, you can go to the Abyss. Do penguins and use penguin points to do this. Don't forget to include tears of Guthix because this xp will definitely be fast and useful Old School RS Gold. An alternative option would be to make use of the Abyss which is self-explanatory or to make earth runes by using the FoG gloves, and Digsite pendants.