The current Guild Bracket system, ranks Guilds in a bracket, based on their point score. This point score is tied to a bracket since, as an extreme example, 200,000 points in bracket 1 is a lot harder to attain than 200,000 points in bracket 100. For this reason, we decided to err on the side of caution with movement of guilds through brackets, not allowing a guild to jump up (or down) more than 2 brackets in a single week. We may change that in future, to allow more movement, but at the moment we don't have anything to announce.
Your guild's initial placement in the brackets would have taken your guild's level and current placement in the guild-trophy leaderboard when you first registered for guild wars. As a newer guild, that will certainly mean starting some way from the top, but given the 1-3 years most top guilds took to establish themselves, we feel that 6-10 months to rise up the brackets for a new guild is not unreasonable.
How bracket calculations work
The bracket calculation for Guild Wars is based on a number of factors including, but not limited to, how well each guild performed in their bracket (standardized by the general difficulty of that bracket), the position each guild finished within their bracket (positions 1 & 2 are awarded small bonuses, while positions 9 & 10 are penalized somewhat), as well as (to a lesser degree) the general makeup & progress of the individual guild.
This means it is possible you might see yourself with more points than a guild in a higher bracket but NOT move up to replace them, and there could be a number of reasons for this, including the fact that the higher bracket was considered more difficult than yours, or even that a team in a lower bracket than you had an amazingly good week and leapfrogged past you.