I keep reading posts discussing a kind of "civilisation progress" as one of the important coming features of RW. If I get it correctly (and correct me if I don't), it should be some kind of "career mode" or vaguely RPG oriented path which would lead the player, mainly on the technology side, from pre-historic tools and techniques to modern day technologies.
From one side, this might be a good thing: it seems to appeal many users and would give a sense of purpose, which is motivating; particularly if, as I assume, it will be fairly articulated and with a good number of steps and/or a reasonably wide and deep technology tree. In other words, if it does not turn out to merely be a varnish or a pretext.
From another side, however, this 'evolutionary' perspective is only one of the ways to look at the sandbox world concept and has some consequences. It mostly depends on how it will implemented and about this we can only speculate. However, some consideration can be made.
1) If it will require enough commitment and engagement to be rewarding, it risks to distract users from sophisticated or ingenuous or 'beautiful' building and crafting tasks. If everybody is busy advancing in technology (maybe looking for rare items which unlock this or that knowledge), then the aesthetic or realistic achievements one can already see in the game as it is now would definitely suffer. We may risk to see the same cave, the same pyramid, the same [put you item here] over and over again, because they are the shortest way to proceed to the next technology advance.
2) This "career mode" would not appeal to everyone; possibly, given what it is possible now in RW, a good number of players came (or stayed) precisely because of the freedom and variety RW allows in building and may not appreciate to be constrained along a given path (I for one certainly would not).
3) It would heavily affect multiplayer interaction. If every player of a server is required (or only has the means) to use the same materials (initially only dirt and stone, I imagine, later bronze, more later iron and so on), the server will become encumbered with rather similar replicas of the same things over and over again and everybody will be busy on his own path, paying little attention to the others. If, rather, the server will advance in technology as a whole, the first comers will have all the fun (or all the boredom, according to the individual tastes) and the late comers will find many (or most) of the steps already accomplished.
4) Or it might be possible to specialize, who knows. This could be stimulating and suit individual preferences: one player would specialize and advance in carpentry, another in metallurgy or farming or herding and so on, leading to trading and some complex form of interaction. Fine! Except for the fact that, by choice, RW has no big central server where many players gather and any specialization is likely to be found, but only many user-maintained servers, many of which are going to have a limited number of players and may end up with a limited number of specializations.
One can continue, but I think the pattern should be clear.
For what is worth, if this progress concept is indeed implemented, my suggestion is to make it optional or one of the possible modes, leaving a more 'pure' sandbox mode still available, so that one can start with photovoltaic panels or carbon fiber already available, if one likes so, being free not to use them if one want to recreate an ancient Egypt or mediaeval Saxon environment (side note for clarity: I make a distinction between a 'pure', 'human' sandbox mode and a 'godly' mode like the Creative one we have now: the latter is basically cheating, while the former should keep some degree of realism).
Thanks for reading, M.