De Beers has scheduled sightholder meetings in July and August, which is where they sell the rough diamonds to cutters. Industry expectations are that there will be significant price increases for rough diamonds and that the expected increases will probably take place in August rather than July. Traditionally De Beers announces in advance what the range of increases will be but that information has not been released, resulting in anticipation of double digit increases in for some groups of diamonds.
Price increase announcements for rough diamonds are usually scheduled ahead of the three major industry trade shows (Basel in March, JCK Las Vegas in June, Hong Kong in September). Price increases tend to be the greatest for larger diamonds since those are the items with the biggest differential between supply and demand. The last major price increase was in May with average prices increasing about 8% but some four-carat and above diamonds increasing over 20% in one day. Production of small diamonds tends to be more in line with demand so they have seen relatively small price increases.
The price increases for polished diamonds tend to follow close behind the rough diamond price increases so the likely timeframe is August or September. If you are planning a large diamond purchase in the next few months, I would suggest taking action sooner rather than later. We do not know when the retail price increases will occur, for what types of diamonds, or how much the price increases will be, but all the signs are that they will go up near the end of summer. It would be a shame for a consumer to pay 5-10% more just because they waited a few weeks too long to make their purchase, especially if they have been made aware of the impending price increase.